1. Field of the Invention
The present invention relates to an apparatus for image projecting, and more particularly, to an apparatus for image projecting to form a plurality of R, G, B color signals on a panel by using an optical-switch having a non-square matrix type structure.
The present application is based on Korean Patent Application No. 2002-24209 filed on May 2, 2002, which is incorporated herein by reference.
2. Description of the Prior Art
A projector is an apparatus for image projecting that shows an image by projecting an input image signal on a screen. The image projecting apparatus is mainly used for presenting in a meeting room, in a projector in a cinema, and in a home theater.
A method for projecting an image on a screen after magnifying the image shown on a liquid crystal display (LCD) or a cathode ray tube (CRT) with a lens has been conventionally used to realize a big screen. However, this method only magnifies an image but does not provide a clear image. To solve the above problem, an image projecting apparatus applying a DMD (Digital Micro-mirror Device) panel is now used.
DMD is an optical-switch using a micro-mirror. The micro-mirror controls the reflection of light in accordance with an input image signal. Also, the DMD applies a digital method, thus color reproduction of the image signal is good and brightness is high. Moreover, it does not require A/D or D/A conversion, thus images are clearly realized.
FIG. 1 is a view showing a basic structure of a conventional apparatus for image projecting using a color wheel.
Referring to FIG. 1, the apparatus for image projecting using the color wheel has a light source 10, a color wheel 20, a DMD panel 30 and a projecting lens 40. In FIG. 1, an optical passage of white light is shown as one dotted line.
The light source 10 emits white light by using an arc lamp or a laser. The color wheel 20 rotates (shown as the direction of an arrow) by a rotating means (not shown), and it is divided into R(red), G(green) and B(blue) regions.
The white light emitted from the light source 10 is separated as R, G, B beams by the R, G, B region of the color wheel 20. The DMD panel 30 is composed of a plurality of micro-mirrors 30a. The R, G, B beams separated for each wavelength are projected to the DMD panel 30 and reflected at the micro-mirrors 30a. Reflected R, G, B beams penetrate the projecting lens 40 and create an image on a screen.
FIG. 2 is a view showing a basic structure of an apparatus for image projecting having an optical-switch of a 3×3 matrix structure.
The apparatus for image projecting 200 of FIG. 2 has been already invented by the inventor of the present invention that is discussed in this specification, but it has not been disclosed to the public yet.
Referring to FIG. 2, the apparatus for image projecting 200 has a light source 110, a first light transmission unit 120, an optical-switch unit 130, a second light transmission unit 140, square-beam generation units 150, a panel 160 and a projecting lens unit 170. Moreover, the optical passages of R, G, and B laser beams in the optical-switch unit 130 are shown by a one-dotted line, a two-dotted line and a three-dotted line respectively.
The light source 110 emits a plurality of monochromatic lights having different wavelengths from each other, and in this embodiment, R, G, and B laser beams will be used as the monochromatic lights. The light transmission unit 120 has a plurality of first optical fibers 122a, 122b and 122c and a plurality of first collimating lenses 124a, 124b and 124c. The first optical fibers 122a, 122b and 122c allow R, G, and B laser beams to pass therethrough, and the first collimating lenses 124a, 124b and 124c focus the laser beams transmitted through the optical fibers to the optical-switch unit 130.
The optical-switch unit 130 has optical switches 130a to 130i arranged in the 3×3 matrix structure. Each of the optical switches 130a to 130i selectively reflects the focused laser beams to output ports 135a, 135b and 135c. 
The laser beams reflected from the optical switches 130a to 130i of the optical-switch unit 130 are incident in second collimating lenses 142a, 142b and 142c through the output ports 135a, 135b and 135c, respectively.
The second light transmission unit 140 has the plurality of second collimating lenses 142a, 142b and 142c and a plurality of second optical fibers 144a, 144b and 144c. The R, G and B laser beams focused to the second optical fibers 144a, 144b and 144c by the second collimating lenses 142a, 142b and 142c are respectively transmitted to light tubes 154a, 154b, and 154c of square-beam generation unit 150.
The square-beam generation unit 150 has a plurality of first lenses 152a, 152b and 152c, a plurality of light tubes 154a, 154b and 154c, and a second lens 156. The light tubes 154a, 154b and 154c convert laser beams split by the first lenses 152a, 152b and 152c into a square beam. The second lens 156 re-splits the converted laser beam.
The panel 160 is a DMD panel. The panel 160 receives the split R, G and B laser beam thereby respectively forming R, G and B color strips at one section among three sections of the panel 160.
The three R, G and B color strips on the panel 160 are formed by the manipulation of the optical-switch unit 130, and one image is created as the same color strip is formed three times at different positions that are upper, middle and lower sections of the panel 160.
The panel 160 digitalizes and time-divides the R, G and B color strips and reflects them at a predetermined angle. The reflected image of the entire panel is projected onto a screen through the projecting lens 170 and the image is realized. The projecting lens 170 is installed facing the panel 160.
The described conventional apparatus for image projecting 100 creates an image by using the color wheel 20, and in this case, the amount of light used in DMD panel 30 is one third of the entire amount. This is because the R beam passed through the R region of the color wheel 20 is evenly projected to the entire DMD panel 30 but G and B beams are blocked by a color filter and not used. It is the same when G and B beams are projected.
The color wheel method can use one third of incident white light, and thus the luminance of the image is lowered to one third. In other words, the entire amount of the light is decreased as the white light emitted from the light source is projected to DMD panel 30 after passing through the color wheel and as a result, light efficiency is lowered as well. Furthermore, the luminance of the created image cannot be maximized.
In addition, the apparatus for image projecting 200 of FIG. 2 already proposed by the inventor of the present invention creates an image by using an optical switch of a 3×3 matrix structure, thus the light efficiency of the apparatus 200 is greater than that of an optical system using a color wheel. However, in the apparatus for image projecting 200, the ends of each color strip formed at an upper, middle and lower layer of the panel 160, are overlapped, and thus the boundary of the color signals are not clear. In this case, an image realized on a screen has an extra line.